Added a param so allow for propogation of trace_timestamp for catchin…

…g pipeline_execution file

nextflow.config

@@ -173,6 +173,7 @@ env {
 process.shell = ['/bin/bash', '-euo', 'pipefail']
 
 def trace_timestamp = new java.util.Date().format( 'yyyy-MM-dd_HH-mm-ss')
+params.trace_timestamp = trace_timestamp
 timeline {
     enabled = true
     file    = "${params.tracedir}/execution_timeline_${trace_timestamp}.html"